As shown in FIG. 1, a patient's spinal column 2 includes twenty-six bones called vertebrae 4 which protect the spinal cord. While the shape and/or size of each vertebra 4 varies depending on the placement, loading, posture, and/or pathology within spinal column 2, each vertebra 4 is composed of cancellous bone, which is a spongy type of osseous tissue. The cancellous bone of each vertebra 4 is then covered by a thin coating of cortical bone, which is a hard and dense type of osseous tissue. An intervertebral disc 6 is positioned between each pair of adjacent vertebrae 4 in spinal column 2. Each disc 6 forms a fibrocartilaginous joint between adjacent vertebrae 4 so as to allow relative movement between adjacent vertebrae 4. Beyond enabling relative motion between adjacent vertebrae 4, each disc 6 acts as a shock absorber for spinal column 2.
Each disc 6 comprises a fibrous exterior surrounding an inner gel-like center which cooperate to distribute pressure evenly across each disc 6, thereby preventing the development of stress concentrations that might otherwise damage and/or impair vertebrae 4 of spinal column 2. Discs 6 are, however, subject to various injuries and/or disorders which may interfere with a disc's ability to adequately distribute pressure and protect vertebrae 4. For example, disc herniation, degeneration, and infection of discs 6 may result in insufficient disc thickness and/or support to absorb and/or distribute forces imparted to spinal column 2. Disc degeneration, for example, may result when the inner gel-like center begins to dehydrate, which may result in a degenerated disc 8 having decreased thickness. This decreased thickness may limit the ability of degenerated disc 8 to absorb shock which, if left untreated, may result in pain and/or vertebral injury.
While pain medication, physical therapy, and other non-operative conditions may alleviate some symptoms, such interventions may not be sufficient for every patient. Accordingly, various procedures have been developed to surgically improve patient quality of life via abatement of pain and/or discomfort. Such procedures may include, discectomy and fusion procedures, such as, for example, anterior cervical interbody fusion (ACIF), anterior lumbar interbody fusion (ALIF), direct lateral interbody fusion (DLIF) (also known as XLIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF). During a discectomy, all or a portion of a damaged disc, e.g., a degenerated disc 8, is removed via an incision, typically under X-ray guidance.
Following the discectomy procedure, a medical professional may determine an appropriate size of interbody device 10 (FIG. 2) via one or more distractors and/or trials of various sizes. Each trial and/or distractor may be forcibly inserted between adjacent vertebrae 4. Upon determination of an appropriate size, one or more of an ACIF, ALIF, DLIF, PLIF, and/or TLIF may be performed by placing an appropriate interbody device 10 (e.g., a cage, spacer, block) between adjacent vertebrae 4 in the space formed by the removed degenerated disc 8. Placement of such interbody devices 10 within spinal column 2 may prevent spaces between adjacent vertebrae 4 from collapsing, thereby preventing adjacent vertebrae 4 from resting immediately on top of one another and inducing fracture of vertebra 4, impingement of the spinal cord, and/or pain. Additionally, such interbody devices 10 may facilitate fusion (e.g., bone to grow together) between adjacent vertebrae 4 by stabilizing adjacent vertebrae 4 relative to one another. Accordingly, as shown in FIG. 2, such interbody devices 10 often may include one or more fixation members such as, for example, screws 12 extending through interbody device 10 and into adjacent vertebrae 4.
Often, following the removal of the distractor and/or trial, a medical professional must prepare one or more bores or holes in a vertebra 4 intended to receive screws 12. Such holes may be formed with the aid of a separate drill guide positioned proximate or abutting vertebra 4 and inserting a drill therethrough. Alternatively, such holes may be formed free hand, without the use of a drill guide. Further, since spinal column 2 is subject to dynamic forces, often changing with each slight movement of the patient, such screw(s) 12 have a tendency to back out (e.g., unscrew) and/or dislodge from interbody device 10, thereby limiting interbody device's 10 ability to stabilize adjacent vertebrae 4, and consequently, promote fusion. Additionally, if screw(s) 12 back out and/or dislodge from interbody device 10, they may inadvertently contact, damage, and/or irritate surrounding tissue. Further, interbody device 10 is commonly comprised of a radiopaque material so as to be visible in situ via x-ray and other similar imaging modalities. However, such materials may impede sagittal and/or coronal visibility, thereby preventing visual confirmation of placement and post-operative fusion.
Thus, there remains a need for improved interbody devices, associated systems, and methods relating thereto.